Hibernate 一对一外键双向关联

最新推荐文章于 2020-08-19 16:04:43 发布

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#java #数据库 #开发工具

本文介绍了一对一外键关联的实现方式，并通过具体的数据库表结构、对象模型、映射文件及测试代码展示了如何在Hibernate中实现这种关联。具体包括创建Person与Address表并设置外键约束，定义Person与Address类之间的关联关系。

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Hibernate 一对一外键双向关联

一对一外键关联是一对多外键关联的特例，只是在多的一方加了个唯一性约束。

一、模型

一个人对应一个地址。

/*==============================================================*/
/* DBMS name: MySQL 5.0 */
/* Created on: 2008-12-9 0:12:54 */
/*==============================================================*/

drop table if exists address;

drop table if exists person;

/*==============================================================*/
/* Table: address                                               */
/*==============================================================*/
create table address
(
   id                   bigint not null auto_increment comment 'ID',
   detail               varchar(120) not null comment '详细地址',
   personid             bigint comment '人的ID',
   primary key (id)
)
type = InnoDB;

alter table address comment '地址';

/*==============================================================*/
/* Table: person                                                */
/*==============================================================*/
create table person
(
   id                   bigint not null auto_increment comment 'ID',
   name                 varchar(24) not null comment '姓名',
   primary key (id)
)
type = InnoDB;

alter table person comment '人';

alter table address add constraint FK_Reference_4 foreign key (personid)
references person (id) on delete restrict on update restrict;

二、对象模型

public class Person implements java.io.Serializable {

  private Long id;
  private String name;
  private Address address;

public class Address implements java.io.Serializable {
  private Long id;
  private Person person;
  private String detail;

三、映射文件

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
  <class name="entity.Person" table="person">
    <id name="id" type="java.lang.Long">
      <column name="id" />
      <generator class="identity" />
    </id>
    <property name="name" type="java.lang.String">
      <column name="name" length="24" not-null="true">
        <comment>姓名</comment>
      </column>
    </property>
    <one-to-one name="address" cascade="all" />
  </class>
</hibernate-mapping>

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
  <class name="entity.Address" table="address" catalog="testdb">
    <id name="id" type="java.lang.Long">
      <column name="id" />
      <generator class="identity" />
    </id>
    <property name="detail" type="java.lang.String">
      <column name="detail" length="120" not-null="true">
        <comment>详细地址</comment>
      </column>
    </property>
    <many-to-one name="person" class="entity.Person"
      fetch="select" unique="true">
      <column name="personid">
        <comment>人的ID</comment>
      </column>
    </many-to-one>
  </class>
</hibernate-mapping>

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
                    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
                    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">


<hibernate-configuration>

  <session-factory>
    <property name="connection.username">root</property>
    <property name="connection.url">
      jdbc:mysql://localhost:3306/testdb
    </property>
    <property name="dialect">
      org.hibernate.dialect.MySQLDialect
    </property>
    <property name="connection.password">xiaohui</property>
    <property name="connection.driver_class">
      com.mysql.jdbc.Driver
    </property>
    <property name="show_sql">true</property>
    <property name="format_sql">true</property>
    <mapping resource="entity/Person.hbm.xml" />
    <mapping resource="entity/Address.hbm.xml" />

  </session-factory>

</hibernate-configuration>

四、测试

import org.hibernate.Transaction;

import entity.Address;
import entity.Person;

import utils.HibernateSessionFactory;

public class Test {
  public static void main(String[] args) {
    savePerson();
  }

  public static void savePerson() {
    Person person = new Person("张三");
    Address address = new Address("XX街X号");
    person.setAddress(address);
    address.setPerson(person);

    Session session = HibernateSessionFactory.getSession();
    Transaction tx = session.beginTransaction();
    session.save(person);
    tx.commit();
  }
}

运行日志：

Hibernate:
        insert
        into
                person
                (name)
        values
                (?)
Hibernate:
        insert
        into
                testdb.address
                (detail, personid)
        values
                (?, ?)